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The new film "Daybreakers," which opens Friday, is set in 2019, after a global virus outbreak has transformed most of the world's population into vampires. This is not good news for the small remaining population of humans, who become the sole source of blood. Vampires are of course very popular in books and on the silver screen, especially recently. But are they real?

In the mainstream media and pop culture, the vampire character is very alluring, with its elements of power, romance, mysticism, eroticism, and immortality. Given the vampires' popularity, it's not surprising that here are many people who claim to be vampires—often as part of the Goth-inspired vampire subculture.

People are drawn to the vampire subculture for the same reasons they are drawn to any subculture: for a sense of community of like-minded enthusiasts. There's a wide variety of activities and levels of participation, from vampire-themed book clubs to secret bloodletting rituals. Some people wear capes; other have vampire fang dental implants. Most vampire enthusiasts engage in harmless role-playing, though now and then murderers with a fascination with the occult or vampirism will make the news.

As for real vampires, there are of course some parasitic animals that feed off the blood of other animals. The vampire bat (Desmodus rotundus) is an obvious example, but other bloodsucking vampires include the lamprey, tick, leech, and female mosquito.
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Humans actually consuming blood for sustenance is another matter.

A few people claim to regularly drink other people's blood, and though the human digestive system isn't well adapted for digesting blood, small quantities of blood may be harmless and are merely broken down into proteins, iron, and amino acids. The real risk — assuming the vampire has a willing donor — is of contracting blood-borne diseases.

While relatively few people claim to be true vampires, some claim to be "psychic vampires." We all know people who can be difficult or emotionally draining, but that's not necessarily what "psychic vampires" are. Instead they are people who claim to drain or tap into the human body's latent "energy systems" (what some call chakra or chi).

While this is an interesting idea, scientists and doctors have never been able to locate or even verify the existence of this supposed "energy." Since there's no evidence that the bodily or psychic energy exists in the first place, there's no way to prove that a "psychic vampire" is in fact draining that energy. Any claims of "psychic vampirism" can likely be explained by imagination or playacting.

That a significant community of people believe that human vampires (psychic or otherwise) actually exist is not unusual; after all, many people also believe in the existence of angels, ghosts, Bigfoot, aliens, and other entities never proven real. Vampires, thankfully, remain safely between the covers of books.